ABUJA, Nigeria (AP) — Nigeria’s president on Saturday declared a state of emergency in parts of Africa’s most populous nation, after a recent slew of deadly attacks blamed on a northern-based radical Muslim sect killed dozens of people, as separate communal clashes in the country’s southeast left more than 40 dead.

President Goodluck Jonathan declared an indefinite state of emergency in four states, which would all allow security agencies there to make arrests without proof and conduct searches without warrants. He also ordered the closure of international borders near the affected areas.

They include parts of northeastern state of Yobe and the central states of Plateau and Niger, all hit by the Christmas Day attacks that left at least 42 people dead, for which a radical sect known as Boko Haram claimed responsibility. Attackers targeted churches and one of the state offices of Nigeria’s secret police.

The president also declared a state of emergency in parts of the northeastern state of Borno, a stronghold of the feared Islamic sect.

“What began as sectarian crises in the northeastern parts of the country has gradually evolved into terrorist activities in different parts of the country with attendant negative consequences on our national security,” Jonathan said.

“(The state of emergency) means extra powers to security agencies in those areas,” said National Security Adviser Owoye Azazi, who also told journalists in Abuja that it would last “until the situation improves.”

Jonathan also said Saturday that he has directed top security officials to set up a special counterterrorism unit to fight the growing threat posed by Boko Haram.

Earlier in the year, an Aug. 26 bombing of the United Nations headquarters in Nigeria’s capital Abuja killed 24 people and wounded 116 others. The sect claimed responsibility for that attack.

The Christmas attacks come a year after a series of Christmas Eve bombings in central city of Jos in the nation’s “middle belt,” where the country’s largely Muslim north meets its largely Christian south. Last year’s Christmas attacks claimed by the militants left at least 32 dead and 74 wounded.

“Terrorism is a war against all of us,” Jonathan said as he spoke during an address on national television on Saturday. “I call on all Nigerians to join hands with government to fight these terrorists.”

The sect, some of whose members are believed to have links to al-Qaida, wants to impose Islamic Shariah law across Nigeria.

The U.S. Embassy had warned U.S. citizens late Friday to exercise caution in Nigeria.

“Violent extremist attacks have continued in various locations, including the states of Bauchi, Borno, Gombe, Kaduna, Kano, Niger, Plateau, and Yobe, resulting in numerous casualties,” the warning read.

Boko Haram’s widening terror attacks, though, are only further intensifying religious and ethnic divisions in Nigeria. In this nation of more than 160 million people, thousands have died in recent years in communal fighting pitting machete-wielding neighbors against each other.